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The aqueous iron(IV) ion, FeIVaqO2+, generated from O3 and Feaq2+, reacts rapidly with various oxygen atom acceptors (sulfoxides, a water-soluble triarylphosphine, and a thiolatocobalt complex). In each case, FeIVaqO2+ is reduced to Feaq2+, and the substrate is oxidized to a product expected for oxygen atom transfer. Competition methods were used to determine the kinetics of these reactions, some of which have rate constants in excess of 107 M-1 s-1. Oxidation of dimethyl sulfoxide (DMSO) has k = 1.26 × 105 M-1 s-1 and shows no deuterium kinetic isotope effect, k(DMSO-d6) = 1.23 × 105 M-1 s-1. The FeIVaqO2+/sulfoxide reaction is the product-forming step in a very efficient Feaq2+-catalyzed oxidation of sulfoxides by ozone. This catalytic cycle, combined with labeling experiments in H218O, was used to determine the rate constant for the oxo-group exchange between FeIVaqO2+ and solvent water under acidic conditions, kexch = 1.4 × 103 s-1.
Pestovsky et al. (Wed,) studied this question.